A new study published in the Public Library of Science (PLos One) led by Professor Zeki of the Wellcome Laboratory of Neurobiology at University College London revealed that neurologically, "love" and "hate" are similar.

Although emotional opposites, it appears that some of the nervous structures in the brain responsible for hate are the same as those used during feelings of romantic love. Like love, hate is often seemingly irrational and can lead to similar acts of extreme behaviour - both heroic and evil.

One would think that both love and hate would be entirety driven by the limbic system, as this is the seat of our emotion and intuition. But Professor Zeki's work demonstrates that a part of the brain called the putamen is also involved. The putamen sits at the centre of the brain and appears to provide connections between the lower parts of the brain, such as the basal stem, and the upper parts of the brain in the cerebral cortex. The putamen is already known to be involved in the perception of contempt and disgust and may also be part of the motor system involved in movement and action.

However, although the circuitry is similar, the way in which it is used for both love and hate is different. One major difference appears to be in the fact that large parts of the cerebral cortex - associated with judgment and reasoning - become de-activated during love, whereas only a small area is deactivated in hate.

This may seem surprising since hate can also be an all-consuming passion like love. But in romantic love, the lover is often less critical and judgmental about their partner whereas it is more likely that in the context of hate the hater may want to exercise judgment in calculating moves to harm, injure or otherwise exact revenge. Therefore the rational, cerebral functions stay activated in order to make these decisions.

Interestingly, Professor Zeki found that the activity of some of the brain structures in response to a hated face is proportional in strength to the amount of hate the person felt, maybe therefore allowing the subjective state of hate to be objectively quantified.

The study also speculated that while the "love circuit" seems to be programmed for loving just one person, the "hate circuit" appears to be capable of targeting groups of people based on their race, religion or even the football club they support.

The fact that the cerebral brain appears to be less involved in love may give some substance to the saying "love is blind". On the other hand, this research suggests that the "hate circuit" is far more calculating and much more complex.